WASHINGTON — In a long-shot victory that could help define the conservative tilt of the Senate, tea-party-backed Ted Cruz defeated an establishment Republican on Tuesday in the hard-fought GOP primary runoff in Texas.

The outcome is not expected to tip the balance of power in the Senate, which is controlled by the Democrats; the Texas seat being vacated is already held by a Republican.

But Cruz's win over Lt. Gov. David Dewhurst provides another example of the tea party movement's influence on voters and turnout — even for a candidate who has never held elected office.

"It's been fascinating to watch," said Sen. John Cornyn of Texas, who holds the state's other Senate seat and runs the GOP campaign arm in the Senate. He called Cruz's ascent "well-earned," adding, "Part of what it says is people are mad atWashington, D.C. They're mad at what they perceive to be the establishment. And they want some change."

No shortage of heavy-hitting surrogates threw their political might behind the two candidates in a costly showdown. More than $40 million was spent, including $14 million from outside groups, according to records compiled by the Center for Responsive Politics.

Sarah Palin rallied over the weekend for Cruz; Gov. Rick Perry spent one of the last days alongside Dewhurst.

Cruz will face Democrat Paul Sadler, a former state representative, in November, but is expected to have the advantage in the Republican-leaning state.

The seat was opened by the upcoming retirement of Republican Sen. Kay Bailey Hutchison. Dewhurst, who has been the state's lieutenant governor since 2003, became the early favorite.

But enthusiasm from national tea party groups propelled Cruz's feisty campaign, and he forced the runoff after Dewhurst failed to win 50% of the vote in the spring primary.

The son of a Cuban immigrant, Cruz, 41, is far from the Washington outsider his upstart candidacy might convey — a point the Dewhurst campaign tried to amplify as outside polls showed Cruz making gains.

The state's former solicitor general, Cruz is a graduate of Princeton and Harvard Law School. He became the first Latino to clerk for a chief justice of the Supreme Court before working for the Federal Trade Commission, the Justice Department and the 2000 GOP presidential ticket of George W. Bushand Dick Cheney. More recently he has been in private practice in Houston, where he lives with his wife and two daughters.

His arrival in the Senate would bolster the tea party flank, which could emerge from the fall election as a growing force in the chamber even if Republicans fail to net the handful of seats needed to wrest the majority from Democrats this fall.

Tea-party-aligned Richard Mourdock in Indiana had already ousted a longtime Republican senator in that state's primary. Conservative stalwart Sen. Jim DeMint (R-S.C.) championed that campaign as well as Cruz's.

Stuart Rothenberg, editor of the nonpartisan Rothenberg Political Report, wrote Tuesday that the Texas candidates held few ideological differences — both want small government and have traditional values.

"The difference between the two men is simple: Cruz is not willing to compromise even if it means being irrelevant to the legislative process," Rothenberg wrote.

A wealthy businessman, Dewhurst poured $11 million from his own fortune into the race, but that was matched by outside groups seeking to influence the outcome.

The conservative Club for Growth spent more than $5 million against Dewhurst, and the Texas Conservatives Fund spent as much against Cruz, according to the Center for Responsive Politics.

"The false narrative continues to be written that the tea party is dead," said Amy Kremer, chairwoman of the Tea Party Express. "But the tea party is alive and ready to own 2012."